Fuel pump runs 4 - 5 seconds then electricity shuts offs whether fuel lines hooked up or not.

I just purchased a 1992 LT1 AT that had been stored outside for 3 + years. Tank had several gallons of water in it. Drained all gas & cleaned tank, new in line filter, cleaned pump inlet filter, removed cleaned & flushed fuel rails & lines. Electricity to pump shuts off after 4-5 seconds even with high pressure line disconnected and battery at 12.5 volts. If power fed directly to pump it runs continually without problems.